Microstructures and mechanical properties of spray-formed and squeeze-cast Al-25Si-0.89Cu1.0Ni-0.84Mg alloys in solutionized and aged conditions

The microstructures and mechanical properties of spray-formed and squeeze-cast Al-25Si-0.89Cu-1.0Ni-0.84Mg alloys in solutionized and aged conditions were compared. DSC analysis was used to study the degree of supersaturation between the spray-formed and squeeze-cast alloys, and the tensile properties of extruded spray-formed alloy in various heat treatment conditions were investigated. The as-spray-formed alloy exhibits more uniform and finer microstructures than the assqueeze-cast alloy. The Al2Cu was the main phase involved in the solutionizing and aging heat treatment. DSC analysis showed the spray-formed alloy had higher degree of supersaturation than the squeeze-cast alloy. For the same heat treatment condition, the matrix microhardness of spray-formed alloy is higher than that of squeeze-cast alloy. The aging hardening curves reveal two peaks and the time to peaks for the spray-formed alloy is shorter than that for the squeeze-cast alloy. The peak-aged spray-formed alloy exhibits an ultimate strength of 366.0 MPa, a yield strength of 235.3 MPa and an elongation of about 3.4%.